The present invention relates to a vehicle fuel tank arrangement and to a method for managing the supply of fuel to a vehicle engine, said fuel comprising at least a first fluid and a second fluid.
In some cases, it may be advantageous to supply a vehicle engine with a fuel which is a mixture of two or more fluids.
For example, using a dual fuel composed of gasoline and diesel can have positive impacts on the overall consumption or on the engine functioning, especially by reducing knocking and/or by improving ignition.
Since the composition of the optimal fuel changes as a function fit the vehicle operational conditions, it has been proposed not to use a fuel having a predetermined and fixed composition but to create the appropriate mixture depending on said conditions. Therefore, it is known to provide a tank for each fluid which will form part of the fuel supplied to the vehicle engine, and to adapt the fluids ratio in the fuel according to the conditions. Alternatively, there may be provided a single tank including a dedicated compartment for each fluid.
Since the respective quantities of fluids which are consumed depend on the operational conditions, one significant weakness of this implementation is that, most of the time, one of the tanks or compartments may be emptied while at quite large quantity of fluid remains in another tank or compartment. Then, it is necessary to fill the empty compartment whereas it would have been possible to drive for a longer time before filling the other compartment. This results in a more frequent need to refill the vehicle, which is not fully satisfactory for the driver.
Of course, it is theoretically possible to increase the volume of the tanks, but this is in practice not, always possible as the amount of space available on the vehicle is often limited or could be used for other purposes.
It therefore appears that, from several standpoints, there is room for improvement in systems for supplying fuel to a vehicle engine.
It is desirable to provide an improved system and method for managing the supply of fuel—comprising at least a first fluid and a second fluid—to a vehicle engine which can overcome the drawbacks of the prior art.
More precisely, it is desirable to provide such a system and method that make it possible to increase the vehicle autonomy, i.e. to increase the vehicle mileage between two fuel fluids refill, without a significant impact on the required space.
To that end, the invention relates to a vehicle fuel tank arrangement for a fuel comprising at least a first fluid and a second fluid, the tank arrangement comprising:                a tank;        a partition wall arranged inside the tank in order to create at least a first compartment for storing the first fluid and a second compartment for storing the second fluid.        
Such vehicle fuel tank arrangement is characterized in that the position of the partition wall inside the tank can be changed to set the volume of the first compartment, respectively the second compartment, to a predetermined value.
The system may further comprise an actuator which is coupled to the partition wall and which is capable of changing the position of the partition wall inside the tank to set the volume of the first compartment, respectively the second compartment, to a predetermined value.
Having a partition wall which can be appropriately positioned, the storage arrangement and system according to the invention make it possible to optimize the respective amounts of the various fluids contained in the tank, and therefore to increase the vehicle autonomy for a given volume of the tank.
In concrete terms, the position of the partition wall can be predetermined depending on the coming vehicle operational conditions, which can be estimated. The partition watt is then positioned accordingly, as a function of predictable data, typically at least one operational parameter.
At the next service station, the driver will only have to fill up the compartments at their maximum with the appropriate fluids. The volumes of the first and the second fluids when the tank is refilled are set by the position of the partition wall. Said position is not necessarily changed until the next stop for refilling one of the compartments. During this period, the ratio of the fluids in the fuel preferably corresponds to the volume ratio in the tank. Indeed, the volume ratio is set based on an estimation of fluid depletion ratio in the compartments. The fluid depletion ratio can be fixed during the period, meaning that the engine is operating with a fuel mixture having the same composition, but, alternatively it can vary during that period to adapt to the engine operation to the vehicle operational conditions at a given time. In the latter case, the fluid depletion ratio estimation is preferably an estimation of the mean ratio for the period until next refill.
The term “position” can both refer to the shape of the partition wall—which is a feature of the partition wall itself and/or to the location of said partition wall—this feature relating to the partition wall with respect to the tank.
According to a second aspect, the invention concerns a method for managing the supply of fuel to a vehicle engine, said method comprising:                providing an arrangement as previously described;—predicting the respective consumptions of the fluids contained in the fuel, based on at least one operational parameter;        before the compartments are refilled, changing the position of the partition wall according to said prediction.        
Optimally, the position for the partition wall is set so that the respective volumes of the fluids in the compartments fall below a minimum threshold substantially at the same time.
By loading the right ratio of fluids, the vehicle autonomy is increased for a given total volume of fluids. Indeed, the number of times the driver needs to stop to fill-up the compartments is reduced, so the time period or distance between two refilling is increased.
The phrase at the same time does not mean exactly simultaneously, but at moments that are close, so as to minimize the period of time when one compartment is nearly empty while the other one still contains enough fluid to supply to the vehicle engine. For example, it can be envisaged that when the volume of one compartment drops below a minimum threshold, then the volume of the other compartment(s) is not more than 10% above the corresponding minimum threshold.
The minimum threshold may be expressed as a percentage of the volume of the compartment for the current setting of the partition wall position. Alternatively, it could be expressed as a certain quantity of remaining fluid in the relevant compartment. The threshold could vary depending on the volume of the compartment for the current setting of the partition wall position.
The minimum threshold, i.e. the predetermined value when a refill is needed or will soon be needed, generally generates a signal for the vehicle driver. The minimum threshold may be different for each compartment, and may generate its own signal for the driver.
These and other features and advantages will become apparent upon reading the following description in view of the drawing attached hereto representing, as non-limiting examples, embodiments of an arrangement according to the invention.